"I'm enjoying the possibility of making a difference in private life," Sink, 65, said Friday citing her foundation, Florida Next, which focuses on promoting entrepreneurs.

Sink's decision not to run was widely expected in Florida political circles, as she showed little sign of putting together a campaign and was up front about her ambivalence and her family's opposition. But until Friday, the former Bank of America leader and former state chief financial officer continued to keep the door open and several times pushed back her deadline for announcing a decision.

"There were many factors," said Sink, who made up her mind last weekend at a family gathering in North Carolina to celebrate her father's 90th birthday.

"There wasn't one thing, but I felt it was time to give an indication because anyone running for an office like governor, especially on the Democratic side, has to be thinking about putting together the resources and it takes time to raise money," said Sink, whose decision was complicated by the sudden death late last year of her husband, Bill McBride, the Democratic gubernatorial nominee in 2002.

Former state Sen. Nan Rich of Broward County announced a year ago she is running for the Democratic nomination but has shown little traction and raised little money.

Former Republican Gov. Crist is expected to announce his bid for the Democratic nomination in October. Without a well-known name like Sink in the primary, his path is much easier.

"I loved working with Alex on the Florida Cabinet and I'm sure it won't be the last time we work together," Crist said in a statement after her announcement. "Florida needs Alex Sink and I'm excited about what's happening at her Florida NEXT Foundation."

U.S. Sen. Bill Nelson remains an unlikely potential candidate, but he has not entirely closed the door on running.

Sink lost to Rick Scott by just over 1 percentage point in 2010, despite being outspent dramatically and facing a Republican tidal wave across the country. Still, many Democrats complained that Sink ran an anemic, excessively cautious campaign against a weak Republican who had run a company that paid the largest fine in U.S. history for Medicare fraud.

And consider this: When Jeb Bush narrowly lost the 1994 gubernatorial election to Lawton Chiles, Florida Republicans united solidly around Bush for his second campaign in 1998. There was no sign Sink enjoyed similarly widespread loyalty.

Sink, who's headed to China on Sunday on a United Way trip, said she expects to spend "some hours" with Rich and, should he run, Crist, with an eye toward endorsing in the expected primary. She has called Crist a "disaster" of a potential Democratic nominee, but more recently softened her tone.

"Now that Alex Sink has opted out of the gubernatorial race, will she stand with Florida's leading liberal Nan Rich? Anything other than full-throated support for Senator Rich is an implicit endorsement of Charlie Crist, a candidate she called a 'disaster,' " Florida GOP chairman Lenny Curry said in a statement. "The Republican Party of Florida is more than happy to run the campaign that Alex Sink would have run against Charlie Crist, who oversaw the second-highest jump in unemployment in the country and was close political allies with criminals and felons."

Sink did not rule out endorsing Crist.

"I have a lot of questions to ask. I have a lot of opinions about running the race," she said. "We need to have confidence that our candidate shares our values. As time goes on, I'm going to be looking to see what kind of support they're able to pull together and I'll be listening very carefully to their visions for Florida's future."

Sink has kept a relatively low profile since her 2010 defeat, but said Friday she intends to speak up more often about Gov. Scott's "missteps."

"Anybody who says we're not going to let people go into our health departments to help Florida families sign up for health insurance, I think he's just downright mean. And he needs to be called out," she said.

Rich called Sink to ask for her endorsement, noting that she endorsed Sink in 2010 (though Sink faced no serious primary opponent). "Her decision obviously frames the race between Rick Scott and me or — if Charlie decides to run — between Charlie Crist and me in the primary," Rich said. "I welcome the opportunity to demonstrate my credentials to Florida voters and present Florida voters a clear choice between my lifelong commitment to working and the middle class versus either of them."